buffer.cpp

00001 /*buffer.cpp creates the circular buffer array and contains functions
00002 responsible for pushing new data on to the queue and also pulling data
00003 from it. It also contains the function to workout the moving average of
00004 the 10 values stored within the circular buffer*/
00005 
00006 #include "mbed.h"
00007 #include "rtos.h"
00008 #include "buffer.h"
00009 
00010 //Creates a struct array, using the custom struct that holds the acceleration measurements.
00011 AccelData circular_buffer_array[10];
00012 
00013 int rear = 0;
00014 int front = 0;
00015 int32_t sumX;
00016 int32_t sumY;
00017 int32_t sumZ;
00018 int32_t averageX;
00019 int32_t averageY;
00020 int32_t averageZ;
00021 
00022 Mutex mutex2;
00023 //Pushes data on to buffer using modulo operation.
00024 void log_push(AccelData data) {
00025     mutex2.lock();
00026 
00027     rear = (rear + 1) % 10;
00028 
00029     if (rear == front) {
00030      front = (front + 1) % 10;
00031   }
00032 
00033     circular_buffer_array[rear] = data;
00034      mutex2.unlock();
00035 }
00036 
00037 //Retrieves a single data struct using the argument to specify which.
00038 AccelData log_get(int index)
00039 {
00040     
00041   AccelData record;
00042   record = circular_buffer_array[(front + index) % 10];
00043 
00044   return record;
00045 
00046 }
00047 
00048 /*This function loops through the array and calculates the average.
00049 It clears the sum totals each time around so that the average is
00050 updated with the new value pushed on to the buffer, creating a 
00051 moving average*/
00052 void print_averages(){
00053 
00054     while(1){
00055          mutex2.lock();
00056     for (int i = 0; i < 10; i++) {
00057 
00058       AccelData entry = log_get(i);
00059       sumX += entry.x;
00060       sumY += entry.y;
00061       sumZ += entry.z;
00062       
00063       /*The two lines below can be uncomented to show the circular buffer working by
00064       outputting the contents of the buffer every time a peice of data is pushed on to it.
00065       This also makes it possible to verify the average is correct.*/
00066       
00067       //printf("LSM6DS0 [acc/mg]:      %6ld, %6ld, %6ld\r\n", entry.x, entry.y, entry.z);
00068       //printf("\r\n");
00069       
00070     }
00071 
00072     averageX = sumX / 10;
00073     averageY = sumY / 10;
00074     averageZ = sumZ / 10;
00075     printf("average [acc/mg]:      %6ld, %6ld, %6ld\r\n", averageX, averageY, averageZ);
00076     printf("\r\n");
00077     sumX = 0;
00078     sumY = 0;
00079     sumZ = 0;
00080     mutex2.unlock();
00081 }
00082 }